PC - Binocular Vision 2 Vergence - Week 2

Question 1

What is the vergence of an eye when it has no EOM innervation?

Answer 1

17 beyond parallel

Question 2

What is the tonic vergence of an eye?

Answer 2

Parallel or slightly esophoric

Question 3

What is the vergence of an eye in the absence of stimuli (no light)?

Answer 3

physiological position of rest.

Question 4

Name 5 tests to measure vergence.

Answer 4

Prentice card
Maddox rod
Von graefe
Cover test
Maddox wing

Question 5

True or false

Von graefe is the ideal test for children

Answer 5

False

Question 6

Define vergence facility, and how its measured.

Answer 6

Speed and accuracy of the vergence system to uptake a convergence or divergence response on demand.
Measured using prism flippers, similar to accommodative facility

Question 7

Name 3 anatomical factors that influence the vergence system.

Answer 7

Size
Shape of the globe
Position of EOM insertion

Question 8

Name 3 neurological factors that influence the vergence system.

Answer 8

Any lesions affecting innervation of cranial nerve III, IV, and VI.

Question 9

Name 5 general factors that influence the vergence system.

Answer 9

Fatigue
Alcohol
Tobacco
Medications
Prisms in glasses

Question 10

Name the 6 types of vergence responses.

Answer 10

Fusional
Proximal awareness
Accommodative
Tonic
Voluntary (convergence)
Vergence adaptation

Question 11

Describe tonic vergence.

Answer 11

Eyes are 17^ beyond parallel when all innervation to EOMs are cut.
Tonic vergence brings EOMs back to parallel or slightly esophoric.

Question 12

What can be said of tonic vergence?

Answer 12

It is the physiological position of rest (in the dark as well).

Question 13

Define vergence posture, and describe 5 means of measuring it.

Answer 13

Vergence posture is heterophoria, measured by:
Prentice card
Von Graefe
Maddox rod
Cover test
Maddox wing (antiquated)

Question 14

Name the test to measure vergence range/amplitude.

Answer 14

Positive and negative relative convergence

Question 15

Name the test to measure vergence facility.

Answer 15

BI and BO flipper challenge

Question 16

Define vergence posture.

Answer 16

How accurately the eyes point relative to the visual stimulus location

Question 17

What is the preferred means of measuring vergence posture (heterophoria) in school-age children?

Answer 17

Prentice card

Question 18

Which is more repeatable, maddox rod or Von Graefe?

Answer 18

Maddox rod

Question 19

True or false

Von Grafe is the preferred method of measuring phoria in children.

Answer 19

False

Question 20

What is one advantage of maddox wing above all other tests?

Answer 20

It can detect cyclophoria, and is sometimes used when it is suspected.

Question 21

What is the main disadvantage of the maddox wing?

Answer 21

Inability to control accommodation.

Question 22

Define vergence amplitude/range.

Answer 22

The capacity of the vergence system, and how much it can converge/diverge on demand.

Question 23

Describe how PRC and NRC are carried out (2).

Answer 23

Use the prentice card and the diamond for fixation. Use the prism bars, and add more ^D, measuring blur, break, and recovery.
Can also be done using the phoropter head, set to converging, and more prisms added using the risley prism.

Question 24

Are the PRC/NRC tests objective or subjective?

Answer 24

Subjective, requiring patient input.

Question 25

Define vergence facility.

Answer 25

How quickly and efficiently the vergence system can change to uptake convergence or divergence on demand.

Question 26

Describe the test for measuring vergence facility.

Answer 26

Pretince card diamond used for fixation, prism flippers used, BO12^D and BI3^D.

Question 27

What is the normal value for posture/phoria at distance and near?

Answer 27

Distance - 1exoP ±1^D

Near - 3exoP ±3^D

Question 28

What is the normal value for PRC at distance and near?

Answer 28

Distance - 10/16/10

Near - 10/16/10

Question 29

What is the normal value for NRC at distance and near?

Answer 29

Distance - 10/16/10

Near - -/6/4

Question 30

What is the normal value for vergence facility?

Answer 30

15 cycles/min

Question 31

Can accommodation and vergence be tested independently?

Answer 31

No, they are interlinked, and one cannot be tested without considering the other.